1. Field of the Invention
The present invention relates to a technique for immobilizing a biological substance to stabilize the biological substance. More particularly, the present invention relates to a particle having a mesopore loaded with a biological substance. The particle can be used in a biosensor.
2. Description of the Related Art
An enzyme is known to have a three-dimensional protein structure that is liable to change by heat or in a certain environment and lose its inherent function. Various methods have been investigated to treat an enzyme or a protein in a stable manner. In one of the methods, an enzyme or a protein is supported by a solid surface. For example, an immobilized enzyme is put into practical use.
For example, an enzyme is immobilized on silica prepared by a sol-gel method, fused quartz, a porous inorganic substance, or a porous organic polymer material. In a recent proposition, an enzyme is immobilized on a mesoporous material prepared using a detergent micelle as a template, particularly mesoporous silica. Japanese Patent Laid-Open Nos. 2000-139459 and 2002-95471 describe such a technique.
However, known techniques for immobilizing an enzyme to mesoporous silica have several problems. Specifically, mesoporous silica, such as MCM-41 or SBA-15 disclosed in Japanese Patent Laid-Open No. 2000-139459 or 2002-95471, has a small pore size reserved only for a small protein. Furthermore, mesoporous silica, such as SBA-15, has tubular pores that are longitudinally oriented in a rod-shaped particle. Thus, the tubular pores have a large aspect ratio (the ratio of the depth to the diameter of a pore). A protein or substrate molecule therefore poorly diffuses into the pores. In addition, the openings on the surface are small in number. Hence, such mesoporous silica accommodates only a smaller amount of protein.